1. Field of the Disclosure
The present disclosure generally relates to methods for handling, treating, and disposing of drilling cuttings from drilling operations. More particularly, the present disclosure relates to methods for desalinating drill cuttings and using desalinated drill cuttings in post-drilling operations.
2. Background Art
In drilling operations for the exploration of oil and gas, a liquid slurry known as drilling mud is used for maintenance and lubrication of the borehole created during the drilling operation. Typically, the drilling mud system of a well includes a mud holding tank at the well surface located on or adjacent to the drilling rig and a network of pumps, mixers, and mud supply lines. During drilling operations, drilling mud is pumped from the mud holding tank, through the mud supply lines, down through the well bore and circulated at a desired rate, and is returned to the surface of the well bore. The returned drilling mud carries with it drill cuttings from the bottom of the borehole produced as drilling advances. When the circulating drilling mud, along with the carried drill cuttings is returned to the surface, it is delivered to a screening device known as a shaker that serves as a sieve for removing the carried drilling cuttings from the drilling mud. When the drill cuttings have been removed from the drilling mud by the shaker, the drilling mud is returned to the mud storage tank for reuse. The drill cuttings separated from the drilling mud are collected and conveyed to storage tanks for treating and disposal.
The storage and disposal of drill cuttings produced at a drilling location may present a number of problems. The drill cuttings removed from the borehole are typically comprised of shale, sand, hard clays, or shell, and they are often coated with, or contain, residual contaminants from the drilling mud of from the borehole. The drill cuttings and their contaminants present environmental concerns that must be addressed during their disposal.
Transporting the drill cuttings from a rig site to a disposal facility is also a concern because of the costs associated with transporting the bulky, heavy cuttings boxes to and from the well location. Additionally, drill cuttings typically contain oil, petroleum distillates, and other environmentally unsuitable contaminants and often must undergo some treatment to remove or render inert any associated contaminants prior to their disposal. Such treatment is time consuming and expensive because it is typically conducted away from the rig location.
In some drilling operations, new waste management techniques (e.g., closed loop dewatering) now allow onsite drill cutting processing that may substantially decrease drill cutting volume. At such drilling operations, it may be beneficial to dispose of the drill cuttings onsite. Typically, onsite drill cutting disposal consists of plowing (i.e., land-farming) cuttings into the land, such that the cuttings stay on the land during storms. However, such land-farming methods are only available if the cuttings are found to be non-hazardous (e.g., contain less than 3000 mg/kg of chlorides and/or less than 1000 mg/L of oil) according to the laws of the local governing agency.
Many localities have separate laws that regulate the disposal of drilling cuttings if the drilling operation is located on a wetland. Currently, many jurisdictions do not allow the land-farming of drill cuttings on recognized wetlands. Instead, the drill cuttings have to removed and properly disposed of outside the drill site.
In still other jurisdictions, if drill cuttings are found to be hazardous (i.e., contain greater than 3000 mg/kg of chlorides and/or greater than 1000 mg/L of oil) according to the laws of the local governing agency, the drill cuttings may be buried onsite. In such a drilling operation, pits may be created at the drilling site and the drill cuttings buried therein. Buried drill cuttings are buried so as to not cause the pollution of ground water or sub-surface water bearing formations. To prevent contamination as a result of the buried cuttings, the pits may have to be lined, chemicals may have to be injected, and the pits may have to be covered with earth or other substrate. In many drilling operations, the burial of drill cuttings is time consuming, potentially environmentally dangerous, and cost inefficient.
In other drilling operations, including operations that drill through large salt deposits, hazardous cuttings may contain large amounts of chlorides that may require desalinization prior to disposal. Desalinization operations may include use of chemical treatments and/or other operations that are time consuming, labor intensive, and expensive. Alternatively, in certain operations, other expensive methods of remediating drill cuttings may be used including, for example, cuttings re-injections. However, these alternative remediation methods may also be time consuming, labor intensive, and expensive.
Accordingly, there exists a need for an environmentally safe and cost efficient system and method for desalinating drill cuttings from drilling operations.